Optical imaging system

ABSTRACT

An optical imaging system includes a first lens having an object-side surface that is convex; a second lens having a refractive power; a third lens having a refractive power; a fourth lens having a refractive power; a fifth lens having a refractive power and an object-side surface that is concave; and a sixth lens having a refractive power and an object-side surface that is concave, wherein the first lens through the sixth lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane, and the optical imaging system satisfies the conditional expressions 0.7&lt;TL/f&lt;1.0 and TL/2&lt;f1, where TL is a distance from the object-side surface of the first lens to the imaging plane, f is an overall focal length of the optical imaging system, and f1 is a focal length of the first lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 16/114,514, filed on Aug. 28, 2018, which claimsthe benefit under 35 USC 119(a) of Korean Patent Application No.10-2017-0137676 filed on Oct. 23, 2017, in the Korean IntellectualProperty Office, the entire disclosure of which is incorporated hereinby reference for all purposes.

BACKGROUND 1. Field

This application relates to a telescopic optical imaging systemincluding six lenses.

2. Description of Related Art

A telescopic optical system designed capture an image of a subject at along distance has a significant size. For example, a ratio (TL/f) of atotal length (TL) of the telescopic optical system to an overall focallength (f) of the telescopic optical system is 1 or more. Therefore, itis difficult to mount a telescopic optical system in a small electronicproduct such as a mobile communications terminal or other portabledevice.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, an optical imaging system includes a first lenshaving an object-side surface that is convex; a second lens having arefractive power; a third lens having a refractive power; a fourth lenshaving a refractive power; a fifth lens having a refractive power and anobject-side surface that is concave; and a sixth lens having arefractive power and an object-side surface that is concave, wherein thefirst lens through the sixth lens are sequentially disposed in numericalorder from an object side of the optical imaging system toward animaging plane of the optical imaging system so that there is a first airgap between the first lens and the second lens, a second air gap betweenthe second lens and the third lens, a third air gap between the thirdlens and the fourth lens, a fourth air gap between the fourth lens andthe fifth lens, and a fifth air gap between the fifth lens and the sixthlens, and the optical imaging system satisfies the conditionalexpressions 0.7<TL/f<1.0 and TL/2<f1, where TL is a distance from theobject-side surface of the first lens to the imaging plane, f is anoverall focal length of the optical imaging system, and f1 is a focallength of the first lens.

The first lens may have a positive refractive power.

The second lens may have a negative refractive power.

The fifth lens may have a negative refractive power.

An object-side surface of the second lens may be convex.

An object-side surface of the fourth lens may be concave.

An image-side surface of the fifth lens may be concave.

There may be an inflection point on either one or both of theobject-side surface of the fifth lens and an image-side surface of thefifth lens.

An image-side surface of the sixth lens may be convex.

An object-side surface of the third lens or an object-side surface ofthe fourth lens may be spherical.

In another general aspect, an optical imaging system includes a firstlens having an image-side surface that is concave; a second lens havinga refractive power; a third lens having a refractive power; a fourthlens having a refractive power; a fifth lens having a refractive power;and a sixth lens having a refractive power and an object-side surfacethat is concave, wherein the first lens through the sixth lens aresequentially disposed in numerical order from an object side of theoptical imaging system toward an imaging plane of the optical imagingsystem so that there is a first air gap between the first lens and thesecond lens, a second air gap between the second lens and the thirdlens, a third air gap between the third lens and the fourth lens, afourth air gap between the fourth lens and the fifth lens, and a fifthair gap between the fifth lens and the sixth lens, and the opticalimaging system satisfies the conditional expression 0.7<TL/f<1.0, whereTL is a distance from an object-side surface of the first lens to theimaging plane, and f is an overall focal length of the optical imagingsystem.

The optical imaging system may further satisfy the conditionalexpression 0<D45/TL<0.2, where D45 is a distance from an image-sidesurface of the fourth lens to an object-side surface of the fifth lens.

The optical imaging system may further satisfy the conditionalexpression 1.5<Nd6<1.7, where Nd6 is a refractive index of the sixthlens.

The optical imaging system may further satisfy the conditionalexpression f2/f<−0.6, where f2 is a focal length of the second lens.

The optical imaging system may further satisfy the conditionalexpression 2.0<f/EPD<2.7, where EPD is an entrance pupil diameter of theoptical imaging system.

The optical imaging system may further satisfy the conditionalexpression |f2/f3|<1.3, where f2 is a focal length of the second lens,and f3 is a focal length of the third lens.

In another general aspect, a optical imaging system includes a firstlens having a refractive power; a second lens having a refractive power;a third lens having a refractive power; a fourth lens having arefractive power; a fifth lens having a refractive power; and a sixthlens having a refractive power; wherein the first lens through the sixthlens are sequentially disposed in numerical order from an object side ofthe optical imaging system toward an imaging plane of the opticalimaging system, the refractive power of the second lens and therefractive power of the fifth lens have a same sign that is opposite toa sign of the refractive power of the first lens, the optical imagingsystem satisfies the conditional expression 0.7<TL/f<1.0, where TL is adistance from the object-side surface of the first lens to the imagingplane, and f is an overall focal length of the optical imaging system.

The first lens may have a positive refractive power, and the second lensand the fifth lens each may have a negative refractive power.

An object-side surface of the first lens may be convex, an object-sidesurface of the fifth lens may be concave, and an object-side surface ofthe sixth lens may be concave.

An image-side surface of the second lens may be concave, and animage-side surface of the sixth lens may be concave.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a first example of an optical imagingsystem.

FIG. 2 illustrates aberration curves of the optical imaging systemillustrated in FIG. 1 .

FIG. 3 is a view illustrating a second example of an optical imagingsystem.

FIG. 4 illustrates aberration curves of the optical imaging systemillustrated in FIG. 3 .

FIG. 5 is a view illustrating a third example of an optical imagingsystem.

FIG. 6 illustrates aberration curves of the optical imaging systemillustrated in FIG. 5 .

FIG. 7 is a view illustrating a fourth example of an optical imagingsystem.

FIG. 8 illustrates aberration curves of the optical imaging systemillustrated in FIG. 7 .

FIG. 9 is a rear view of an example of a mobile communications terminalin which an optical imaging system described in this application ismounted.

FIG. 10 is a cross-sectional view of the mobile communications terminalillustrated in FIG. 9 taken along the line X-X′ in FIG. 9 .

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

Throughout the specification, when an element, such as a layer, region,or substrate, is described as being “on,” “connected to,” or “coupledto” another element, it may be directly “on,” “connected to,” or“coupled to” the other element, or there may be one or more otherelements intervening therebetween. In contrast, when an element isdescribed as being “directly on,” “directly connected to,” or “directlycoupled to” another element, there can be no other elements interveningtherebetween.

As used herein, the term “and/or” includes any one and any combinationof any two or more of the associated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Spatially relative terms such as “above,” “upper,” “below,” and “lower”may be used herein for ease of description to describe one element'srelationship to another element as shown in the figures. Such spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,an element described as being “above” or “upper” relative to anotherelement will then be “below” or “lower” relative to the other element.Thus, the term “above” encompasses both the above and below orientationsdepending on the spatial orientation of the device. The device may alsobe oriented in other ways (for example, rotated 90 degrees or at otherorientations), and the spatially relative terms used herein are to beinterpreted accordingly.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

In this application, a first lens is a lens closest to an object (or asubject), while a sixth lens is a lens closest to an imaging plane (oran image sensor). In addition, radii of curvature, thicknesses oflenses, TL, an IMG HT (a half of a diagonal length of the imagingplane), and focal lengths of the lenses are expressed in millimeters(mm). Further, thicknesses of the lenses, gaps between the lenses, andTL are distances measured along optical axes of the lenses. Further, ina description of the shapes of the lenses, a statement that a surface ofa lens is convex means that at least a paraxial region of the surface isconvex, and a statement that a surface of a lens is concave means thatat least a paraxial region of the surface is concave. A paraxial regionof a lens surface is a central portion of the lens surface surroundingthe optical axis of the lens in which light rays incident to the lenssurface make a small angle to the optical axis and the approximationssin θ≈θ, tan θ≈θ, and cos θ≈1 are valid. Therefore, although it may bestated that a surface of a lens is convex, an edge portion of thesurface may be concave. Likewise, although it may be stated that asurface of a lens is concave, an edge portion of the surface may beconvex.

In the examples described in this application, an optical imaging systemincludes six lenses. For example, the optical imaging system may includea first lens, a second lens, a third lens, a fourth lens, a fifth lens,and a sixth lens sequentially disposed in numerical order from an objectside of the optical imaging system toward an imaging plane of theoptical imaging system. The first lens through the sixth lens may bedisposed so that there is a first air gap between the first lens and thesecond lens, a second air gap between the second lens and the thirdlens, a third air gap between the third lens and the fourth lens, afourth air gap between the fourth lens and the fifth lens, and a fifthair gap between the fifth lens and the sixth lens. Thus, an image-sidesurface of one lens may not be in contact with an object-side surface ofa next lens closer to the imaging plane.

The first lens may have a refractive power. For example, the first lensmay have a positive refractive power. One surface of the first lens maybe convex. For example, an object-side surface of the first lens may beconvex.

The first lens may have an aspherical surface. For example, bothsurfaces of the first lens may be aspherical. The first lens may be madeof a material having a high light transmissivity and an excellentworkability. For example, the first lens may be made of plastic.However, a material of the first lens is not limited to plastic. Forexample, the first lens may be made of glass. The first lens may have asmall refractive index. For example, the refractive index of the firstlens may be less than 1.6.

The second lens may have a refractive power. For example, the secondlens may have negative refractive power. One surface of the second lensmay be convex. For example, an object-side surface of the second lensmay be convex.

The second lens may have an aspherical surface. For example, theobject-side surface of the second lens may be aspherical. The secondlens may be made of a material having a high light transmissivity and anexcellent workability. For example, the second lens may be made ofplastic. However, a material of the second lens is not limited toplastic. For example, the second lens may be made of glass. The secondlens may have a refractive index greater than the refractive index ofthe first lens. For example, the refractive index of the second lens maybe 1.65 or greater.

The third lens may have a refractive power. For example, the third lensmay have a positive refractive power or a negative refractive power. Thethird lens may have a meniscus shape in which one surface is concave andthe other surface is convex. For example, an object-side surface of thethird lens may be convex and an image-side surface thereof may beconcave, or the object-side surface of the third lens may be concave andthe image-side surface thereof may be convex.

The third lens may have a spherical surface. For example, theobject-side surface of the third lens may be spherical, and theimage-side surface thereof may be aspherical. The third lens may be madeof a material having a high light transmissivity and an excellentworkability. For example, the third lens may be made of plastic.However, a material of the third lens is not limited to plastic. Forexample, the third lens may be made of glass. The third lens may have arefractive index greater than the refractive index of the first lens.For example, the refractive index of the third lens may be 1.6 orgreater.

The fourth lens may have a refractive power. For example, the fourthlens may have a positive refractive power or a negative refractivepower. One surface of the fourth lens may be concave. For example, theobject-side surface of the fourth lens may be concave.

The fourth lens may have a spherical surface. For example, theobject-side surface of the fourth lens may be spherical, and animage-side surface thereof may be aspherical. The fourth lens may bemade of a material having a high light transmissivity and an excellentworkability. For example, the fourth lens may be made of plastic.However, a material of the fourth lens is not limited to plastic. Forexample, the fourth lens may be made of glass. The fourth lens may havea refractive index that is substantially equal to the refractive indexof the first lens. For example, the refractive index of the fourth lensmay be less than 1.6.

The fifth lens may have a refractive power. For example, the fifth lensmay have a negative refractive power. One surface of the fifth lens maybe concave. For example, an object-side surface of the fifth lens may beconcave. The fifth lens may have an inflection point. For example,either one or both of the object-side surface and an image-side surfaceof the fifth lens may have an inflection point.

The fifth lens may have an aspherical surface. For example, bothsurfaces of the fifth lens may be aspherical. The fifth lens may be madeof a material having a high light transmissivity and an excellentworkability. For example, the fifth lens may be made of plastic.However, a material of the fifth lens is not limited to plastic. Forexample, the fifth lens may be made of glass. The fifth lens may have arefractive index that is substantially equal to the refractive index ofthe first lens and the fourth lens. For example, the refractive index ofthe fifth lens may be less than 1.6.

The sixth lens may have a refractive power. For example, the sixth lensmay have a positive refractive power or a negative refractive power. Onesurface of the sixth lens may be concave. For example, an object-sidesurface of the sixth lens may be concave.

The sixth lens may have an aspherical surface. For example, bothsurfaces of the sixth lens may be aspherical. The sixth lens may be madeof a material having a high light transmissivity and an excellentworkability. For example, the sixth lens may be made of plastic.However, a material of the sixth lens is not limited to plastic. Forexample, the sixth lens may be made of glass. The sixth lens may have arefractive index greater than the refractive index of the first lens.For example, the refractive index of the sixth lens may be 1.6 orgreater.

The aspherical surfaces of the first to sixth lenses are represented byEquation 1 below.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {Jr}^{20}}} & (1)\end{matrix}$

In Equation 1, c is an inverse of a radius of curvature of the lens, kis a conic constant, r is a distance from a certain point on anaspherical surface of the lens to an optical axis of the lens, A to Jare aspherical constants, and Z (or sag) is a distance between thecertain point on the aspherical surface of the lens at the distance rand a tangential plane meeting the apex of the aspherical surface of thelens.

The optical imaging system may further include a filter, an imagesensor, and a stop.

The filter may be disposed between the sixth lens and the image sensor.The filter may block some wavelengths of light. For example, the filtermay block infrared wavelengths of light.

The image sensor may form the imaging plane. For example, a surface ofthe image sensor may form the imaging plane.

The stop may be disposed to control an amount of light incident to theimage sensor. For example, the stop may be disposed between the secondlens and the third lens, but is not limited to this position.

The optical imaging system may satisfy one or more of ConditionalExpressions 1 through 7 below.

0.7<TL/f<1.0  (Conditional Expression 1)

0<D45/TL<0.2  (Conditional Expression 2)

1.5<Nd6<1.7  (Conditional Expression 3)

f2/f<−0.6  (Conditional Expression 4)

2.0<f/EPD<2.7  (Conditional Expression 5)

|f2/f3|<1.3  (Conditional Expression 6)

TL/2<f1  (Conditional Expression 7)

In the above Conditional Expressions 1 through 7, TL is a distance fromthe object-side surface of the first lens to the imaging plane, f is anoverall focal length of the optical imaging system, D45 is a distancefrom the image-side surface of the fourth lens to the object-sidesurface of the fifth lens, Nd6 is a refractive index of the sixth lens,f1 is a focal length of the first lens, f2 is a focal length of thesecond lens, f3 is a focal length of the third lens, and EPD is anentrance pupil diameter of the optical imaging system. The f-number (FNo.) of the optical imaging system is equal to f/EPD, and thus f/EPD inConditional Expression 5 above is equal to the f-number (F No.) of theoptical imaging system. Tables 1, 3, 5, and 7 that appear later in thisapplication list the f-number (F No.) of first to fourth examples of anoptical imaging system described later in this application.

Conditional Expression 1 is a condition for miniaturizing the opticalimaging system. For example, when TL/f is outside of an upper limitvalue of Conditional Expression 1, it is difficult to miniaturize theoptical imaging system, making it difficult to mount the optical imagingsystem in a mobile communications terminal, and when TL/f is outside ofa lower limit value of Conditional Expression 1, it is difficult tomanufacture the optical imaging system.

Conditional Expression 2 is a condition for ensuring both goodtelescopic characteristics of the optical imaging system and goodresolution of the optical imaging system. For example, when D45/TL isoutside of a lower limit value of Conditional Expression 2, it isdifficult to maintain the resolution of the optical imaging system, andwhen D45/TL is outside of an upper limit value of Conditional Expression2, the telescopic characteristics of the optical imaging system aredeteriorated.

Conditional Expression 3 is a condition for improving aberration throughthe sixth lens. For example, when the refractive index of the sixth lensis outside of a numerical range of Conditional Expression 3, it isdifficult to correct astigmatism, longitudinal chromatic aberration, andchromatic aberration of magnification.

Conditional Expression 4 is a condition for ensuring easy manufacturingof the second lens. For example, when f2/f is outside of an upper limitvalue of Conditional Expression 4, the second lens has a large opticalsensitivity, making it difficult to manufacture the second lens.

Conditional Expression 5 is a condition for implementing a brightoptical imaging system.

Conditional Expression 6 is a condition for significantly decreasingaberration through the second lens and the third lens. For example, when|f2/f3| is outside of an upper limit value of Conditional Expression 6,the aberration is increased, thereby decreasing the resolution of theoptical imaging system.

Next, several examples of an optical imaging system will be described.

FIG. 1 is a view illustrating a first example of an optical imagingsystem.

Referring to FIG. 1 , an optical imaging system 100 includes a firstlens 110, a second lens 120, a third lens 130, a fourth lens 140, afifth lens 150, and a sixth lens 160.

The first lens 110 has a positive refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The second lens 120 has a negative refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The third lens 130 has a positive refractive power, an object-sidesurface thereof is concave, and an image-side surface thereof is convex.The fourth lens 140 has a negative refractive power, an object-sidesurface thereof is concave, and an image-side surface thereof isconcave. The fifth lens 150 has a negative refractive power, anobject-side surface thereof is concave, and an image-side surfacethereof is concave. Both surfaces of the fifth lens 150 have inflectionpoints. The sixth lens 160 has a positive refractive power, anobject-side surface thereof is concave, and an image-side surfacethereof is convex. The optical imaging system 100 has a narrow field ofview. For example, the optical imaging system 100 has a field of view of40° or less. In detail, the field of view of the optical imaging system100 is θ=25.32.

The optical imaging system 100 further includes a filter 170, an imagesensor 180, and a stop ST. The filter 170 is disposed between the sixthlens 160 and the image sensor 180, and the stop ST is disposed betweenthe second lens 120 and the third lens 130, but is not limited to thisposition.

FIG. 2 illustrates aberration curves of the optical imaging systemillustrated in FIG. 1 .

Table 1 below lists characteristics of the optical imaging systemillustrated in FIG. 1 , and Table 2 below lists aspherical values of thelenses of the optical imaging system illustrated in FIG. 1 .

TABLE 1 First Example f = 5.75 F No. = 2.28 θ = 25.32° TL = 5.240Surface Radius Refractive Abbe Focal No. Element of CurvatureThickness/Distance Index No. Length S1 First Lens 1.4433 0.9847 1.54456.00 2.645 S2 728.5499 0.2000 S3 Second Lens 13.0590 0.2336 1.661 20.40−3.805 S4 2.1141 0.1285 Stop Infinity 0.1001 S5 Third Lens −36.06760.2356 1.650 21.47 9.663 S6 −5.4150 0.1000 S7 Fourth Lens −12.12690.2300 1.544 56.00 −9.342 S8 8.8765 0.6050 S9 Fifth Lens −47.3505 0.38751.544 56.00 −6.767 S10 4.0230 0.5563 S11 Sixth Lens −10.5945 0.60781.650 21.47 32.233 S12 −7.2239 0.1001 S13 Filter Infinity 0.2100 1.51964.20 S14 Infinity 0.5804 S15 Imaging Plane Infinity −0.0196

TABLE 2 First Radius of Example Curvature K A B C D E F G H J S1 1.443−0.365 0.008 0.017 −0.054 0.141 −0.223 0.197 −0.090 0.016 0.000 S2728.550 0.000 0.055 −0.037 −0.047 0.123 −0.151 0.090 −0.023 0.002 0.000S3 13.059 0.000 0.015 −0.047 0.502 −2.580 7.960 −14.586 15.821 −9.3202.307 S4 2.114 −8.148 −0.007 0.163 −1.304 4.341 −8.515 9.083 −2.452−3.068 1.922 S5 −36.068 84.363 0.007 −0.085 −0.588 1.002 −1.184 1.712−1.247 0.000 0.000 S6 −5.415 −34.536 0.225 0.857 −11.874 91.722 −436.9161301.853 −2356.42 2362.081 −1003.98 S7 −12.127 84.778 0.112 0.274 −0.9666.410 −19.477 31.752 −28.594 11.168 0.000 S8 8.877 98.900 −0.141 0.282−0.566 3.297 −9.778 16.220 −14.129 4.842 0.000 S9 −47.351 99.000 −0.229−0.081 0.695 −2.066 3.613 −3.636 2.059 −0.604 0.071 S10 4.023 −63.019−0.088 −0.035 0.097 −0.139 0.137 −0.082 0.028 −0.005 0.000 S11 −10.595−99.000 −0.102 0.105 −0.069 0.019 0.000 0.001 −0.001 0.000 0.000 S12−7.224 0.000 −0.128 0.124 −0.120 0.095 −0.054 0.020 −0.005 0.001 0.000

FIG. 3 is a view illustrating a second example of an optical imagingsystem.

Referring to FIG. 3 , an optical imaging system 200 includes a firstlens 210, a second lens 220, a third lens 230, a fourth lens 240, afifth lens 250, and a sixth lens 260.

The first lens 210 has a positive refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is convex.The second lens 220 has a negative refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The third lens 230 has a positive refractive power, an object-sidesurface thereof is concave, and an image-side surface thereof is convex.The fourth lens 240 has a negative refractive power, an object-sidesurface thereof is concave, and an image-side surface thereof isconcave. The fifth lens 250 has a negative refractive power, anobject-side surface thereof is concave, and an image-side surfacethereof is concave. Both surfaces of the fifth lens 250 have inflectionpoints. The sixth lens 260 has a positive refractive power, anobject-side surface thereof is concave, and an image-side surfacethereof is convex. The optical imaging system 200 has a narrow field ofview. For example, the optical imaging system 200 has a field of view of40° or less. In detail, the field of view of the optical imaging system200 is θ=24.89.

The optical imaging system 200 further includes a filter 270, an imagesensor 280, and a stop ST. The filter 270 is disposed between the sixthlens 260 and the image sensor 280, and the stop ST is disposed betweenthe second lens 220 and the third lens 230, but is not limited to thisposition.

FIG. 4 illustrates aberration curves of the optical imaging systemillustrated in FIG. 3 .

Table 3 below lists characteristics of the optical imaging systemillustrated in FIG. 3 , and Table 4 below lists aspherical values of thelenses of the optical imaging system illustrated in FIG. 3 .

TABLE 3 Second Example f = 5.60 F No. = 2.43 θ = 24.89° TL = 5.000Surface Radius of Thickness/ Refractive Abbe Focal No. Element CurvatureDistance Index No. Length S1 First Lens 1.4056 0.9417 1.544 56.00 2.510S2 −43.4165 0.1600 S3 Second Lens 11.0320 0.2300 1.661 20.40 −3.745 S42.0239 0.1168 Stop Infinity 0.1000 S5 Third Lens −31.2658 0.2326 1.650421.47 14.507533 S6 −7.3295 0.1000 S7 Fourth Lens −21.7194 0.2300 1.54456.00 −11.052 S8 8.3983 1.0848 S9 Fifth Lens −3.8000 0.2300 1.544 56.00−6.049 S10 25.9530 0.1397 S11 Sixth Lens −10.9009 0.5845 1.650 21.4789.119 S12 −9.3863 0.1002 S13 Filter Infinity 0.2000 1.519 64.20 S14Infinity 0.5576 S15 Imaging Plane Infinity −0.0078

TABLE 4 Second Radius of Example Curvature K A B C D E F G H J S1 1.406−0.350 0.009 0.025 −0.076 0.219 −0.381 0.371 −0.186 0.036 0.000 S2−43.416 0.000 0.074 −0.048 −0.066 0.191 −0.258 0.170 −0.048 0.004 0.000S3 11.032 0.000 0.007 −0.060 0.701 −4.005 13.613 −27.505 32.899 −21.3615.831 S4 2.024 −8.405 0.000 0.211 −1.845 6.688 −14.564 17.127 −5.097−7.031 4.856 S5 −31.266 −99.000 0.001 −0.151 −0.819 1.547 −2.024 3.228−2.592 0.000 0.000 S6 −7.330 80.652 0.208 1.053 −16.708 142.469 −747.2742454.835 −4898.83 5413.925 −2537.00 S7 −21.719 99.000 0.122 0.347 −1.3509.952 −33.312 59.873 −59.445 25.598 0.000 S8 8.398 99.000 −0.026 0.283−0.780 5.214 −16.852 30.585 −29.373 11.099 0.000 S9 −3.800 3.952 0.064−1.153 3.086 −5.298 6.160 −4.674 2.189 −0.569 0.062 S10 25.953 70.4690.096 −0.730 1.856 −2.874 2.725 −1.593 0.561 −0.110 0.009 S11 −10.901−99.000 −0.159 0.496 −0.585 0.325 −0.070 −0.012 0.009 −0.002 0.000 S12−9.386 0.000 −0.233 0.363 −0.375 0.295 −0.177 0.074 −0.019 0.003 0.000

FIG. 5 is a view illustrating a third example of an optical imagingsystem.

Referring to FIG. 5 , an optical imaging system 300 includes a firstlens 310, a second lens 320, a third lens 330, a fourth lens 340, afifth lens 350, and a sixth lens 360.

The first lens 310 has a positive refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The second lens 320 has a negative refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The third lens 330 has a negative refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.One surface of the third lens 330 is a spherical surface and the othersurface of the third lens is an aspherical surface. For example, anobject-side surface of the third lens 330 is a spherical surface, and animage-side surface thereof is an aspherical surface. The fourth lens 340has a positive refractive power, an object-side surface thereof isconcave, and an image-side surface thereof is convex. The fifth lens 350has a negative refractive power, an object-side surface thereof isconcave, and an image-side surface thereof is concave. Both surfaces ofthe fifth lens 350 have inflection points. The sixth lens 360 has apositive refractive power, an object-side surface thereof is concave,and an image-side surface thereof is convex. The optical imaging system300 has a narrow field of view. For example, the optical imaging system300 has a field of view of 40° or less. In detail, the field of view ofthe optical imaging system 300 is θ=24.41.

The optical imaging system 300 further includes a filter 370, an imagesensor 380, and a stop ST. The filter 370 is disposed between the sixthlens 360 and the image sensor 380, and the stop ST is disposed betweenthe second lens 320 and the third lens 330, but is not limited to thisposition.

FIG. 6 illustrates aberration curves of the optical imaging systemillustrated in FIG. 5 .

Table 5 below lists characteristics of the optical imaging systemillustrated in FIG. 5 , and Table 6 below lists aspherical values of thelenses of the optical imaging system illustrated in FIG. 5 .

TABLE 5 Third Example f = 6.00 F No. = 2.65 0 = 24.41° TL = 5.290Surface Radius of Thickness/ Refractive Abbe Focal No. Element CurvatureDistance Index No. Length S1 First Lens 1.4144 0.8510 1.544 56.00 2.657S2 43.0741 0.0500 S3 Second Lens 4.4611 0.2390 1.661 20.40 −8.0591 S42.3883 0.1000 Stop Infinity 0.2000 S5 Third Lens 107.8754 0.2400 1.650421.47 −6.6326 S6 4.1871 0.1674 S7 Fourth Lens −89.6829 0.2300 1.54456.00 206.347 S8 −50.0000 1.0270 S9 Fifth Lens −3.1691 0.2900 1.54456.00 −4.7817 S10 15.3784 0.2648 S11 Sixth Lens −151.2417 0.7458 1.65021.47 12.560 S12 −7.8450 0.0400 S13 Filter Infinity 0.2100 1.519 64.20S14 Infinity 0.6550 S15 Imaging Plane Infinity −0.0200

TABLE 6 Third Radius of Example Curvature K A B C D E F G H J S1 1.414−0.351 0.009 0.020 −0.070 0.193 −0.314 0.290 −0.142 0.027 0.000 S243.074 0.000 0.128 −0.168 −0.043 0.424 −0.775 0.729 −0.348 0.066 0.000S3 4.461 0.000 0.096 −0.159 0.128 −0.643 2.682 −5.660 6.569 −3.906 0.930S4 2.388 −2.596 −0.020 0.168 −1.169 4.180 −8.515 9.083 −2.452 −3.0681.922 S5 107.875 S6 4.187 −23.505 0.104 1.252 −17.486 152.975 −818.9902735.879 −5553.53 6268.187 −3016.83 S7 −89.683 −99.000 0.129 −0.0170.103 0.000 0.000 0.000 0.000 0.000 0.000 S8 −50.000 −99.000 0.154 0.0000.000 0.000 0.000 0.000 0.000 0.000 0.000 S9 −3.169 −2.527 −0.044 0.217−0.907 1.760 −1.927 1.269 −0.500 0.109 −0.010 S10 15.378 22.815 −0.1000.422 −0.991 1.223 −0.909 0.424 −0.122 0.020 −0.001 S11 −151.242 −99.000−0.166 0.427 −0.594 0.453 −0.201 0.051 −0.007 0.000 0.000 S12 −7.8450.000 −0.159 0.198 −0.154 0.055 −0.001 −0.007 0.002 0.000 0.000

FIG. 7 is a view illustrating a fourth example of an optical imagingsystem.

Referring to FIG. 7 , an optical imaging system 400 includes a firstlens 410, a second lens 420, a third lens 430, a fourth lens 440, afifth lens 450, and a sixth lens 460.

The first lens 410 has a positive refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The second lens 420 has a negative refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The third lens 430 has a positive refractive power, an object-sidesurface thereof is convex, and an image-side surface thereof is concave.The fourth lens 440 has a positive refractive power, an object-sidesurface thereof is concave, and an image-side surface thereof is convex.One surface of the fourth lens 440 is a spherical surface, and the othersurface of the fourth lens 440 is an aspherical surface. For example, anobject-side surface of the fourth lens 440 is a spherical surface, andan image-side surface of the fourth lens 440 is an aspherical surface.The fifth lens 450 has a negative refractive power, an object-sidesurface thereof is concave, and an image-side surface thereof is convex.Both surfaces of the fifth lens 450 have inflection points. The sixthlens 460 has a negative refractive power, an object-side surface thereofis concave, and an image-side surface thereof is convex. The opticalimaging system 400 has a narrow field of view. For example, the opticalimaging system 400 has a field of view of 40° or less. In detail, thefield of view of the optical imaging system 400 is θ=25.07.

The optical imaging system 400 further includes a filter 470, an imagesensor 480, and a stop ST. The filter 470 is disposed between the sixthlens 460 and the image sensor 480, and the stop ST is disposed betweenthe third lens 430 and the fourth lens 440, but is not limited to thisposition.

FIG. 8 illustrates aberration curves of the optical imaging systemillustrated in FIG. 7 .

Table 7 below lists characteristics of the optical imaging systemillustrated in FIG. 7 , and Table 8 below lists aspherical values of thelenses of the optical imaging system illustrated in FIG. 7 .

TABLE 7 Fourth Example f = 5.60 F No. = 2.6 6 = 25.07° TL = 5.280Surface Radius of Refractive Abbe Focal No. Element CurvatureThickness/Distance Index No. Length S1 First Lens 1.4365 0.7886 1.54456.00 2.645 S2 186.1834 0.1998 S3 Second Lens 5.9143 0.2341 1.661 20.40−3.780 S4 1.7431 0.1564 S5 Third Lens 4.6972 0.3376 1.6504 21.47 27.295S6 6.1815 0.1677 Stop Infinity 0.1023 S7 Fourth Lens −6.4326 0.25271.544 56.00 13.017 S8 −3.4249 0.1284 S9 Fifth Lens −2.0657 0.3000 1.54456.00 −7.373 S10 −4.4563 0.7231 S11 Sixth Lens −5.0958 0.6336 1.65021.47 −19.746 S12 −8.8027 0.1001 S13 Filter Infinity 0.2100 1.519 64.20S14 Infinity 0.9707 S15 Imaging Plane Infinity −0.0250

TABLE 8 Fourth Radius of Example Curvature K A B C D E F G H J S1 1.436−0.372 0.011 0.013 −0.047 0.130 −0.212 0.192 −0.093 0.017 0.000 S2186.183 0.000 0.070 −0.036 −0.052 0.137 −0.174 0.108 −0.031 0.003 0.000S3 5.914 0.000 0.029 −0.042 0.349 −1.906 6.217 −11.726 12.945 −7.7291.938 S4 1.743 −4.367 −0.020 0.168 −1.169 4.180 −8.515 9.083 −2.452−3.068 1.922 S5 4.697 −62.851 0.026 −0.017 −0.865 2.811 −6.313 8.030−4.260 0.000 0.000 S6 6.181 −99.000 0.141 0.892 −12.279 95.633 −463.9191418.924 −2656.30 2773.752 −1236.64 S7 −6.433 S8 −3.425 9.589 0.0370.199 −0.585 3.521 −10.093 16.342 −14.307 5.023 0.000 S9 −2.066 −8.746−0.130 0.396 −0.247 0.582 −0.969 0.485 0.025 −0.076 0.015 S10 −4.456−58.287 −0.171 0.256 −0.198 0.078 0.060 −0.118 0.068 −0.017 0.002 S11−5.096 −99.000 −0.249 0.187 −0.171 0.127 −0.045 0.003 0.002 −0.001 0.000S12 −8.803 0.000 −0.114 0.012 0.057 −0.096 0.080 −0.038 0.011 −0.0020.000

Table 9 below lists values of Conditional Expressions 1 through 7 of theoptical imaging systems of the first to fourth examples.

TABLE 9 Conditional First Second Third Fourth Expression Example ExampleExample Example TL/f 0.9113 0.8929 0.8817 0.9429 D45/TL 0.1155 0.21700.1941 0.0243 Nd6 1.650 1.650 1.650 1.650 f2/f −0.6617 −0.6688 −1.3432−0.6750 f/EPD 2.28 2.43 2.65 2.60 |f2/f3| −0.3938 −0.2581 1.2151 −0.1385TL/2 2.620 2.500 2.645 2.640

FIG. 9 is a rear view of an example of a mobile communications terminalin which an optical imaging system described in this application ismounted. FIG. 10 is a cross-sectional view of the mobile communicationsterminal illustrated in FIG. 9 taken along the line X-X′ in FIG. 9 .

Referring to FIGS. 9 and 10 , a mobile communications terminal 10includes a plurality of camera modules 30 and 40. A first camera module30 includes a first optical imaging system 500 configured to capture animage of a subject positioned at a short distance away from the mobilecommunications terminal 10, and a second camera module 40 includes asecond optical imaging system 100, 200, 300, or 400 configured tocapture an image of a subject positioned at a long distance away fromthe mobile communications terminal 10.

The first optical imaging system 500 includes a plurality of lenses. Forexample, the first optical imaging system 500 may include four or morelenses. The first optical imaging system 500 is configured to an imageof a subject positioned at a short distance away from the mobilecommunications terminal 10. For example, the first optical imagingsystem 500 may have a wide field of view of 50° or more, and a ratio(h1/Cf) may be 1.0 or h1 is a height of the first optical imaging system500 and is equal to a total length of the first optical imaging system500, and Cf is an overall focal length of the first optical imagingsystem 500.

The second optical imaging system 100, 200, 300, or 400 includes aplurality of lenses. For example, the second optical imaging system 100,200, 300, or 400 may include six lenses. The second optical imagingsystem 100, 200, 300, or 400 is any one of the optical imaging systemsof the first to fourth examples described above. The second opticalimaging system 100, 200, 300, or 400 is configured to capture an imageof a subject positioned at a long distance away from the mobilecommunications terminal 10. For example, the second optical imagingsystem 100, 200, 300, or 400 may have a narrow field of view of 40° orless, and a ratio (h2/f) may be less than 1.0, where h2 is a height ofthe second optical imaging system 100, 200, 300, or 400 and is equal tothe total length TL of the second optical imaging system, and f is theoverall focal length of the second optical imaging system 100, 200, 300,or 400.

The examples described above provide an optical imaging system capableof capturing an image of a subject at a long distance and being mountedin a small terminal.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system comprising: a firstlens having a refractive power; a second lens having negative refractivepower; a third lens having a refractive power; a fourth lens having arefractive power; a fifth lens having a refractive power; and a sixthlens having positive refractive power, wherein the first to sixth lensesare sequentially disposed from an object side to an imaging plane,wherein a radius of curvature of an image-side surface of the secondlens is greater than a radius of curvature of an object-side surface ofthe third lens, and wherein 0.7<TL/f<1.0, where TL is a distance from anobject-side surface of the first lens to the imaging plane, and f is anoverall focal length of the optical imaging system.
 2. The opticalimaging system of claim 1, wherein the fifth lens has negativerefractive power.
 3. The optical imaging system of claim 1, wherein thesixth lens has positive refractive power.
 4. The optical imaging systemof claim 1, wherein the third lens has a concave object-side surface. 5.The optical imaging system of claim 1, wherein the fourth lens has aconcave image-side surface.
 6. The optical imaging system of claim 1,wherein the fifth lens has a concave image-side surface.
 7. The opticalimaging system of claim 1, wherein the sixth lens has a concaveobject-side surface.
 8. The optical imaging system of claim 1, whereinthe sixth lens has a convex image-side surface.
 9. The optical imagingsystem of claim 1, wherein 0<D45/TL<0.2, where D45 is a distance from animage-side surface of the fourth lens to an object-side surface of thefifth lens.
 10. The optical imaging system of claim 1, whereinf2/f<−0.6, where f2 is a focal length of the second lens.
 11. An opticalimaging system comprising: a first lens having a refractive power; asecond lens having negative refractive power; a third lens having aconcave image-side surface; a fourth lens having a refractive power; afifth lens having a refractive power; and a sixth lens having arefractive power, wherein the first to sixth lenses are sequentiallydisposed from an object side to an imaging plane, wherein a radius ofcurvature of an image-side surface of the sixth lens is greater than aradius of curvature of an object-side surface of the sixth lens, andwherein 0.7<TL/f<1.0, where TL is a distance from an object-side surfaceof the first lens to the imaging plane, and f is an overall focal lengthof the optical imaging system.
 12. The optical imaging system of claim11, wherein the first lens has positive refractive power.
 13. Theoptical imaging system of claim 11, wherein the third lens has negativerefractive power.
 14. The optical imaging system of claim 11, whereinthe fourth lens has positive refractive power.
 15. The optical imagingsystem of claim 11, wherein the fifth lens has negative refractivepower.
 16. The optical imaging system of claim 11, wherein |f2/f3|<1.3,where f2 is a focal length of the second lens, and f3 is a focal lengthof the third lens.